User equipment and method for performing downlink and/or uplink power control

ABSTRACT

A user equipment includes a plurality of antennas to receive downlink signals from a base station, a plurality of receiver circuits each coupled to a respective one of the plurality of antennas to process the received downlink signals, an SIR estimation unit to estimate a quality of the received downlink signals, a power loop controller to generate transmit power control commands based on the estimated quality of the received downlink signals, the transmit power control commands being directed to the base station to adjust a power of the downlink signals and a diversity controller to selectively activate and deactivate one or more of the receiver circuits depending on the estimated quality of the received downlink signals.

REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.12/967,180 filed on Dec. 14, 2010.

FIELD

This invention relates to a user equipment (UE) performing downlinkpower control (DLPC), a user equipment performing uplink power control(ULPC), a method for downlink power control of a user equipment, and amethod for uplink power control of a user equipment.

BACKGROUND

In mobile communications between a base station (BS) and a userequipment (UE), diversity receivers are used in the user equipment toimprove the reception of radio signals sent by the base station. Thediversity receivers improve the quality of the received signal. The useof receive diversity, however, leads to significantly increased powerconsumption, considerably reducing the available talk times. Therefore,there is a need to provide a user equipment that efficiently usesbattery power to provide high talk times at high signal quality.

In 3GPP (3^(rd) Generation Partnership Project) standardization,performance requirements are specified for reception of the DPCH(dedicated physical channel) fulfilling the so called “EnhancedPerformance Requirements Type 1”. These Type 1 requirements refer touser equipments using receive diversity (RxDiv, two or more receiveantennas) according to 3GPP Technical Specification TS 25.101 V7.16.0(2009-05), Section 8.3, 8.6, 8.8. In order to fulfill these requirementsit is necessary according to 3GPP to operate the RxDiv receiver all thetime in RxDiv mode, i.e. with both antennas being activated and with thefull receive diversity receiver being activated. The frequency ofoccurrence of call drops which is one of the major quality criteria usedfor finally deployed devices used by network (NW) operators and handsetvendors will be significantly reduced when RxDiv is used because RxDivprovides a considerable SNR gain, e.g. 3 dB minimum without fading andwithout antenna correlation and even larger gains with fading andwithout antenna correlation. On the other hand, the usage of RxDiv,however, leads to significantly increased current consumption, reducingthe talk time considerably.

For these and other reasons there is a need for the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIG. 1 schematically illustrates a user equipment according to oneembodiment.

FIG. 2 schematically illustrates a user equipment according to oneembodiment.

FIG. 3 schematically illustrates a power control system with a userequipment and a base station according to one embodiment.

FIG. 4 schematically illustrates examples of downlink signals and uplinksignals between a base station and a user equipment according to oneembodiment.

FIG. 5 schematically illustrates a state diagram of a system as depictedin FIG. 3 according to one embodiment.

FIG. 6 schematically illustrates a user equipment according to oneembodiment.

FIG. 7 schematically illustrates a performance diagram of a userequipment according to one embodiment depicting a high-windup scenario.

FIG. 8 schematically illustrates a performance diagram of a userequipment according to one embodiment depicting an out-of-sync scenario.

FIG. 9 schematically illustrates a test case for an out-of-sync scenarioin a user equipment according to one embodiment.

FIG. 10 schematically illustrates a test case for a high-windup scenarioin a user equipment according to one embodiment.

FIG. 11 schematically illustrates a performance gain diagram of a userequipment according to one embodiment.

FIG. 12 schematically illustrates a performance diagram of a userequipment according to one embodiment.

FIG. 13 schematically illustrates a further state diagram of a system asdepicted in FIG. 3 according to one embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

It is to be understood that the features of the various exemplaryembodiments described herein may be combined with each other, unlessspecifically noted otherwise.

As employed in this Specification, the terms “coupled” and/or“electrically coupled” are not meant to mean that the elements must bedirectly coupled together; intervening elements may be provided betweenthe “coupled” or “electrically coupled” elements.

User equipments, i.e. devices which include antennas, receiver circuits,transmitters and power loop controllers and which may includesignal-to-interference-ratio (SIR) estimation units, diversitycontrollers and TPC quality estimators are described below.

Antennas are transducers that transmit or receive electromagnetic waves.In other words, antennas convert electromagnetic radiation intoelectrical current, or vice versa. Antennas generally deal in thetransmission and reception of radio waves. Antennas are used in systemssuch as radio communications, wireless LAN, cell phones and mobilecommunications.

Antennas in the user equipment receive downlink radio signals from abase station and convert these signals into electrical signals which arethe received downlink signals.

Radio signals are radio frequency signals that are radiated by a radiotransmitter (sender) with a radio frequency (RF) in the range of about 3Hz to 300 GHz. This range corresponds to the frequency of alternatingcurrent electrical signals used to produce and detect radio waves. RFusually refers to oscillations in electrical circuits.

The use of multiple antennas in a user equipment results in improvedoverall system performance due to the use of diversity techniques.Receiver diversity (RxDiv) or antenna diversity, also known as spacediversity, is any one of several wireless diversity schemes that use twoor more antennas to improve the quality and reliability of a wirelesslink. Often, especially in urban and indoor environments, there is not aclear line-of sight (LOS) between transmitter and receiver. Instead thesignal is reflected along multiple paths before finally being received.Each of these bounces can introduce phase shifts, time delays,attenuations, and even distortions that can destructively interfere withone another at the aperture of the receiving antenna. Antenna diversityis especially effective at mitigating these multipath situations. Thisis because multiple antennas offer a receiver several observations ofthe same signal. Each antenna will experience a different interferenceenvironment. Thus, if one antenna is experiencing a deep fade, it islikely that another has a sufficient signal. Collectively such a systemcan provide a robust link. While this is primarily seen in receivingsystems (Receiver Diversity), the analog has also proven valuable fortransmitting systems (Transmitter Diversity) as well. The use ofmultiple antennas at both transmit and receive results in amultiple-input multiple-output (MIMO) system. The use of diversitytechniques at both ends of the link is termed space-time coding.

Receiver circuits are coupled to a respective antenna in order toprocess the received downlink signal of the antenna. Receiver circuitsmay include Rake receivers and/or equalizers or other suitablereceivers.

Downlink signals are signals transmitted in downlink direction, i.e.from a base station to a user equipment. Downlink signals carry downlinkchannels. In WCDMA a user terminal may be allocated one or more PhysicalData Channels (PDCHs) or Dedicated Physical Data Channels (DPDCHs) whichcarry user bits. A user terminal may also be allocated a PhysicalControl Channel (PCCH) or a Dedicated Physical Control Channel (DPCCH)on which overhead control information is carried to the user, e.g. bitrate information of the associated PDCHs, transmit power control bitsand pilot symbols, which can be used to perform the SIR measurements inthe fast power control loop process. A Dedicated Physical Channel (DPCH)includes Dedicated Physical Data Channels (DPDCHs) and a DedicatedPhysical Control Channel (DPCCH). A user terminal may also be allocatedan F-DPCH (fractional DPCH) channel which carries only transmit powercontrol bits. In case of F-DPCH, the received transmit power controlsymbols must be used to perform quality estimation required for the fastpower control loop process.

Rakes are rake receivers or generalized-rake (G-Rake) receivers whichexploit multi-path information of the received radio signal. A rake canbe utilized to counter the effects of multipath fading. This can beachieved by using several sub-equalizers or “fingers”, that is, severalcorrelators each assigned to a different multi-path component. Eachfinger independently equalizes a single multi-path component, and at alater stage the contribution of some or all fingers are combined inorder to make use of the different transmission characteristics of eachtransmission path. This results is a higher signal-to-noise ratio in amulti-path environment. By using rakes, different paths with differentdelays can be effectively combined to obtain the path diversity gain.Due to narrow transmission pulses and a large transmission bandwidth ofthe radio channel, the resulting inter-symbol interference (ISI) and along delay spread in the characterization of the radio channel may beovercome by using the rake. A rake output signal is provided at anoutput of the rake.

Equalizers equalize effects of the radio channel on the received radiosignal, such as delay or multipath fading by applying the inversechannel impulse response to the received signal in order to reconstructthe original transmitted signal. The inverse of the channel impulseresponse may be stored in an array, e.g. forming an FIR filter and maybe updated by an adaptive algorithm. An estimation of the transmittedsignal is provided as equalized signal at an output of the equalizer.

Receiver circuits may include mixers for mixing the received signalsdown to baseband, demodulators for demodulating the received signals anddecoders for decoding the received signals. Demodulation is the inverseoperation of modulation which is performed in the base stationtransmitter, e.g. a UMTS transmitter. By way of example, the modulationscheme (constellation) in UMTS transmitters is quadrature phase shiftkeying (QPSK) or quadrature amplitude modulation, e.g. 16QAM or 256QAM.Modulation is a process where the transmitted symbols are multipliedwith the carrier signal obtaining a signal to be transmitted.Demodulation is the inverse process multiplying the received signal withthe carrier signal to obtain the original transmitted symbols. Themodulating symbols are called chips, and their modulating rate may, forexample, be 3.84 Mcps.

Transmitters in the user equipment are transmission circuits used fortransmission of the uplink signal to the base station. Uplink signalsare signals transmitted in uplink direction, i.e. from a user equipmentto a base station. The transmitter may transmit uplink signals atdifferent power levels which power levels may be adjusted by a powerloop controller. The transmitter is able to shut power off and to turnpower on. The transmitter may use a transmission antenna or an array oftransmission antennas for transmitting the uplink signal to the basestation.

Signal-to-interference-plus-noise-ratio (SIR) estimation units(sometimes also called SINR) perform estimation of SIR values of thedownlink signals after demodulation. Thesignal-to-interference-plus-noise ratio (SIR) is the quotient betweenthe average received modulated signal power and the sum of the averagereceived interference power and the received noise. The interferencepower may be generated by other transmitters than the useful signal.Interference is anything which alters, modifies, or disrupts a signal asit travels along a channel between a source and a receiver. In WidebandCDMA systems, this kind of interference is frequently called other-cellinterference. Additionally, there is own-cell interference or inter-pathinterference. In a frequency selective transmission channel, the signaltravels from the transmitter to the receiver along differenttransmission paths which are characterized by different propagationdelays and uncorrelated fading. These multiple transmission pathsinterfere with each other, hence the resulting interference is calledinter-path interference.

Power loop controllers are controllers for performing uplink and/ordownlink power control. For uplink power control (ULPC) power loopcontrollers may adjust a power of the uplink signals directed to a basestation based on transmit power control (TPC) commands included indownlink signals from the base station. For downlink power control(DLPC) power loop controllers may generate transmit power control (TPC)commands based on quality estimates (e.g. estimated SIR values) ofdownlink signals and transmit these TPC commands to the base station torequest the base station adjusting a power of the downlink signals.

Power control (PC) is an essential function of cellular CDMA systems.WCDMA is the third generation cellular system (3G) of the 3GPP (3^(rd)Generation Partnership Project) forum. For WCDMA, power control isdefined for the FDD (Frequency Division Duplex) system and for the TDD(Time Division Duplex) system.

The WCDMA air interface is organized in frames of 10 ms duration. Aframe contains 15 time slots and each slot includes one power control(PC) command (up or down), which gives a PC update rate of 1500 Hz. Thetransmitted power has a fixed value during a given time slot. Powercontrol in WCDMA for DPCH channels is a closed-loop PC which is acombination of outer and inner closed loop control. Power control forthe WCDMA may be performed in the power loop controller. The inner (alsocalled fast) closed loop PC adjusts the transmitted power of thedownlink channel in order to keep the received SIR equal to a giventarget. This SIR target is fixed according to the received BLER (BlockError Rate) or BER (Bit Error Rate). The setting of the SIR target(SIR_(target)) is done by the outer loop PC, which is part of the RadioResource Control Layer, in order to match the required BLER. Outer loopPC update frequency is about 10-100 Hz. The BLER target is a function ofthe service that is carried. Ensuring that the lowest possible SIRtarget is used results in greater network capacity. The innerclosed-loop PC of the user equipment measures the received quality onthe downlink channel based on the received SIR and sends transmit powercontrol (TPC) commands on an uplink channel to the base station in orderto request power update of the downlink channel. For F-DPCH channels,the NW sets a quality target for the F-DPCH. The UE autonomously sets aSIR target value and adjusts it in order to achieve the same quality asthe quality target set by NW. The quality target is set as a downlinkTPC command error rate target value for the F-DPCH belonging to theradio link from the HS-DSCH serving cell as signaled by the UTRAN.Hence, for F-DPCH, the TPC command error rate target replaces the BLERtarget used for DPCH channels. This is required since the F-DPCHchannels do not contain any user data which could be used for a BLERmeasurement.

SIR estimation is performed by an SIR estimation unit which may be anelectrical circuit for estimation of SIR. The SIR estimation unitestimates the received power of the downlink channel to be powercontrolled and the received interference and noise on this downlinkchannel. For DPCH channels, the signal power and the interference andnoise power may be estimated by using pilot symbols, i.e., known symbolstransmitted on one or more downlink channels. For F-DPCH channels,quality estimation has to be performed on the TPC symbols. The obtainedSIR estimate, noted SIR_(est), or TPC quality estimate in case ofF-DPCH, may then be used by the power loop controller to generate PCcommands which may be according to DPC Mode 0 or 1 of the 3GPPspecification.

With DPC Mode 0 of 3GPP TS 25.214 V7.15.0 (2010-03), the transmittedpower is updated at each time slot (10/15 ms). It is increased ordecreased by a fixed value: if SIR_(est)>SIR_(target), then the TPCcommand to transmit is “0”, requesting a transmit power decrease; ifSIR_(est)<SIR_(target), then the TPC command to transmit is “1”,requesting a transmit power increase. DPC Mode 1 of 3GPP TS 25.214V7.15.0 (2010-03) is a slight variant of DPC Mode 0 where thetransmitted powers may be updated each three time slots, which simulatessmaller power update steps. The power control step size is a parameterof the fast (inner) closed-loop PC which may be implemented on the powerloop controller. It is equal to 0.5, 1, 1.5 or 2 dB. The power updatestep size may be chosen according to the average mobile speed and otheroperating environment parameters.

Quality estimators are estimation devices for estimating a qualitymeasure of a signal, in particular a quality of transmit power controlcommands included in the downlink signals. The quality measure may be asignal-to-noise ratio (SNR), a signal-to-interference-plus-noise ratio(SIR), an absolute power of the downlink signal measured at the userequipment, an error rate or any other quality measure. The qualityestimator may monitor TPC commands in the received downlink signal overa specified time interval in order to estimate a quality measure. Avalid TPC command is one command which is generated at the base stationin response to the SIR measured from the last uplink signal receivedfrom the user equipment, and that is transmitted in the downlink signalat a power level responsive to the TPC commands in the last uplinksignal received from the user equipment.

The quality measure may be used for “Out-of-Sync” detection between basestation and user equipment. For example, if the user equipment receivesthe downlink signal and determines that, e.g., the TPC command errorrate exceeds some threshold Q_(Qout), e.g. 30% over a measurementinterval of 240 slots (or 160 ms) according to 3GPP, it may detect“Out-of-Sync”. If the user equipment determines that the TPC commanderror rate is less than a threshold Q_(in), e.g. less than 20% over ameasurement interval of 240 slots (or 160 ms) according to 3GPP, it mayconclude that it is “In-Sync”. Upon an “Out-of-Sync” detection the userequipment may turn its transmitter off. Upon an “In-Sync” detection theuser equipment may turn its transmitter on again. Switching on and offthe transmitter may be under the control of the power loop controller.

Diversity controllers are used to control diversity receivers includingreceiver circuits. Diversity receivers enhance reliability by minimizingthe channel fluctuations due to fading. The central idea in diversity isthat different antennas receive different versions of the same signal.The chances of all these copies being in a deep fade is small. Theseschemes therefore make most sense when the fading is independent fromelement to element and are of limited use (beyond increasing the SNR) ifperfectly correlated (such as in line-of-sight conditions). Independentfading would arise, for example, in a dense urban environment where theseveral multipath components add up very differently at each element.

Fading may be modeled as having three components which are path loss,large-scale and small-scale fading. Over fairly long periods the firsttwo components are approximately constant and can be dealt with usingpower control. Furthermore, these components of fading are very close tobeing constant across all elements of the array (perfectly correlated).Diversity combining is specifically targeted to counteract small scalefading, e.g. Rayleigh fading. According to the physical model, fading isassumed to be independent from one element to the next. Diversity“works” because for N elements in the receiving antenna array Nindependent copies of the same signal are received by the diversityreceiver. It is unlikely that all N elements are in a deep fade. If atleast one copy has reasonable power, one should conceivably be able toadequately process the signal.

Each receiver element of a diversity receiver, therefore, receives anindependent sample of the random fading process, i.e., an independentcopy of the transmitted signal. In the diversity receiver theseindependent samples are combined under control of the diversitycontroller in order to achieve the desired goal of increasing the SNRand reducing the BER. The diversity controller may select individualreceiver circuits in the diversity receiver for data processing. Thediversity controller may control the way of combining these samples, forexample selecting “Maximum Ratio Combining” (MRC), i.e. obtainingweights that maximize the output SNR, selecting “Selection Combining”(SC), i.e. choosing the element with the greatest SNR for furtherprocessing or selecting “Equal Gain Combining” (EGC), i.e. setting unitgain at each element. The diversity controller may further control thepower of the diversity receiver by turning off receiver circuits whichprovide poor SNRs or BERs in order to save power and by turning onreceiver circuits which provide good SNRs or BERs in order to improvethe detection quality of the diversity receiver. The diversitycontroller may control the power switching of the receiver circuitsdepending on a quality measure of the quality estimator.

The devices described below may be designed for implementing the UMTS(Universal Mobile Telecommunications System) standard, e.g. one of theRelease 99, 4, 5, 6, 7, 8 and 9 or higher versions of the UMTS standard.The devices may implement a HSPA (High Speed Packet Access) mobiletelephony protocol, such as HSDPA (High Speed Downlink Packet Access)and HSUPA (High Speed Uplink Packet Access). The devices may implementthe HSPA+ (Evolved HSPA) standard. The devices may be designed toimplement the WCDMA (Wideband Code Division Multiple Access) standard.The devices may be designed to implement the LTE (Long Term Evolution)mobile communications standard, the E-UTRAN (Evolved UniversalTerrestrial Radio Access Network) standard, the HSOPA (High SpeedOrthogonal Frequency Division Multiplex Packet Access) standard or theSuper 3G standard defined by 3GPP (Third Generation Partnership Project)standardization organization. Further the devices may be designed toimplement WiMAX (Worldwide Interoperability for Microwave Access)according to the industrial consortium developing test strategies forinteroperability or the IEEE (Institute of Electrical and ElectronicsEngineers) 802.16 (wireless MAN) and 802.11 (wireless LAN) standards.The devices described in the following may also be designed to implementother standards.

The devices may include integrated circuits and/or passives. Theintegrated circuits may be manufactured by different technologies andmay, for example, be designed as logic integrated circuits, analogintegrated circuits, mixed signal integrated circuits, memory circuitsor integrated passives.

FIG. 1 schematically illustrates a user equipment 100 according to oneembodiment, in particular a user equipment which is configured forperforming Downlink Power Control (DLPC). The user equipment 100includes a plurality of antennas, e.g. a first antenna 101 and a secondantenna 102, to receive downlink signals, e.g. a first downlink signal103 and a second downlink signal 104, from a base station 150. The userequipment 100 further contains a plurality of receiver circuits, e.g. afirst receiver circuit 105 and a second receiver circuit 106; each ofthe receiver circuits is coupled to a respective one of the plurality ofantennas. In the embodiment illustrated in FIG. 1, the first receivercircuit 105 is coupled to the first antenna 101, and the second receivercircuit 106 is coupled to the second antenna 102. The receiver circuits105, 106 process the received downlink signals, i.e. the first receivercircuit 105 processes the first downlink signal 103, and the secondreceiver circuit 106 processes the second downlink signal 104.

The user equipment 100 further includes a quality estimation unit 110,which is configured to estimate the quality of the received downlinksignals 103, 104. The estimation may be based on the SIR(signal-to-interference-plus-noise ratio) of pilot symbols included inthe downlink signals 103, 104, and/or may be based on the quality of TPCsymbols included in the downlink signals 103, 104. The qualityestimation unit 110 may be coupled to some or all of the receivercircuits 105, 106 in order to estimate the quality based on outputsignals of the receiver circuits 105, 106. The quality estimation unitmay, for example, estimate a quality value for each of the outputsignals of the receiver circuits 105, 106.

The user equipment 100 further includes a power loop controller 120 anda diversity controller 130. The power loop controller 120 is coupled tothe quality estimation unit 110 and is configured to generate transmitpower control (TPC) commands 122 based on the estimated qualityestimated by the quality estimation unit 110. The transmit power controlcommands 122 are directed to the base station 150 in order to adjust thepower of the downlink signals 103, 104.

The diversity controller 130 is coupled to the quality estimation unit110 and is configured to selectively activate and/or deactivate at leastone of the receiver circuits 105, 106 depending on the estimated qualityvalues. Alternatively, at least one of the antennas 101, 102 may beactivated and/or deactivated by the diversity controller 130 or both,antennas 101, 102 and corresponding receiver circuits 105, 106 may beactivated.

FIG. 2 schematically illustrates a user equipment 200 according to oneembodiment, in particular a user equipment which is configured forperforming Uplink Power Control (ULPC). The user equipment 200 includesa plurality of antennas, e.g. a first antenna 201 and a second antenna202 to receive downlink signals, e.g. a first downlink signal 203 and asecond downlink signal 204 from a base station 250. The user equipment200 further includes a plurality of receiver circuits, e.g. a firstreceiver circuit 205 and a second receiver circuit 206; each of thereceiver circuits is coupled to a respective one of the plurality ofantennas. For example, the first receiver circuit 205 is coupled to thefirst antenna 201, and the second receiver circuit 206 is coupled to thesecond antenna 202. The receiver circuits 205, 206 process the receiveddownlink signals, i.e. the first receiver circuit 205 processes thefirst downlink signal 203, and the second receiver circuit 206 processesthe second downlink signal 204.

The plurality of antennas 201, 202 with corresponding receiver circuits205, 206 for receiving the downlink signals 203, 204 from the basestation 250 may correspond to the respective circuits 101, 102, 105,106, 150 and signals 103, 104 as illustrated in FIG. 1.

The user equipment 200 further includes a power loop controller 220, aTPC quality estimator 240 and a diversity controller 230. The power loopcontroller 220 and the TPC quality estimator 240 are each coupled to theplurality of receiver circuits 205, 206 in order to receive the receiveddownlink signals 203, 204. The diversity controller 230 is coupled tothe TPC quality estimator 240.

The power loop controller 220 adjusts a power of the uplink signals 223transmitted to the base station 250 by a transmitter 260 in the userequipment 200. The power loop controller 220 uses a power adjust signal222 to adjust the power of the transmitter 260 based on transmit powercontrol commands included in the downlink signals 203, 204.

The TPC quality estimator 240 estimates a quality measure of thetransmit power control commands included in the downlink signals 203,204. The quality measure may, for example, be a signal-to-noise ratio, asignal-to-interference-plus-noise ratio (SIR) or an error rate of thepower control commands.

The diversity controller 230 is coupled to the TPC quality estimator 240and is configured to selectively activate and/or deactivate at least oneof the receiver circuits 205, 206 depending on the estimated qualitymeasure. Alternatively, at least one of the antennas 201, 203 may beactivated and/or deactivated by the diversity controller 230 or both,antennas 201, 202 and corresponding receiver circuits 205, 206 may beactivated.

Depending on the estimated quality measure the power loop controller 220may turn off the transmitter 260, e.g. when the quality measure fallsbelow a first (lower) threshold, the power loop controller 220 may turnoff the transmitter 260 in order to avoid the transmitter 260 fromtransmitting uplink signals 223 based on unsecure detected transmitpower control commands in the downlink signals 203, 204. When thequality measure exceeds a second (higher) threshold, the power loopcontroller 220 may turn on the transmitter 260 again because a reliablequality measure indicates a reliable transmit power control command inthe downlink signals 203, 204.

The power loop controller 220 may additionally have the functionality ofthe power loop controller 120 depicted in FIG. 1, and the user equipment200 may additionally include the quality estimation unit 110 of FIG. 1.The diversity controller 230 may additionally have the functionality ofthe diversity controller 130 depicted in FIG. 1. The user equipment 200of FIG. 2 and the user equipment 100 of FIG. 1 may be integrated in thesame device.

FIG. 3 schematically illustrates a power control system with a userequipment 300 and a base station 350 according to one embodiment. Thebase station 350 transmits downlink signals DL1, DL2 by an antenna 351to the user equipment 300. The user equipment 300 includes a pluralityof antennas, e.g. a first antenna 301 and a second antenna 302 toreceive the downlink signals, e.g. the first downlink signal DL1 and thesecond downlink signal DL2, from the base station 350.

The user equipment 300 further includes a plurality of receivercircuits, e.g. a first receiver circuit 305 and a second receivercircuit 306; each of the receiver circuits is coupled to a respectiveone of the plurality of antennas. For example, the first receivercircuit 305 is coupled to the first antenna 301, and the second receivercircuit 306 is coupled to the second antenna 302. The user equipment 300includes a combiner (e.g. a Maximum Ratio Combiner MRC) coupled to theplurality of receiver circuits 305, 306, and combining the receivedsignals from the plurality of receiver circuits, a quality estimationunit 310 (which may be realized as an SIR estimation unit) coupled tothe plurality of receiver circuits 305, 306 and to the combiner MRC, apower loop controller 320 coupled to the plurality of receiver circuits305, 306 and to the combiner MRC. The user equipment 300 includes atransmitter 360 coupled to the power loop controller 320, a qualityestimator 340 coupled to the plurality of receiver circuits 305, 306,and to the combiner MRC, and a diversity controller 330 coupled to theSIR estimation unit 310 and to the TPC quality estimator 340.

The receiver circuits 305, 306 process the received downlink signals,i.e. the first receiver circuit 305 processes the first downlink signalDL1 and the second receiver circuit 306 processes the second downlinksignal DL2.

Each of the receiver circuits 305, 306 includes a demodulator todemodulate the respective received downlink signal and a rake to detectmultipath signals in the respective demodulated received downlinksignal. The combiner combines the detected multipath signals F1 and F2of the first 305 and second 306 receiver circuits in order to provide acombined multipath signal F1+2 which is a combination of the detectedmultipath signals F1, F2 of both receiver circuits 305, 306. Thecombined multipath signal F1+2 has an optimum signal-to-noise ratio. Thedetected multipath signals F1, F2 and the combined multipath signal F1+2may be digital signals having a frame structure with a field of pilotsymbols and/or a field of transmit power control commands (TPC).

The quality estimation unit 310 is configured to estimate the quality ofthe detected multipath signals F1, F2 and the combined multipath signalF1+2 via an SIR estimation. The quality estimation unit 310 may includethree (or any other number of) SIR estimators. A first SIR estimatorSIR_EST1 estimates a first SIR value SIR1 of the detected multipathsignal F1, a second SIR estimator SIR_EST2 estimates a second SIR valueSIR2 of the detected multipath signal F2, and a third SIR estimatorSIR_EST1+2 estimates a third SIR value SIR1+2 of the combined multipathsignal F1+2. The estimation may be based on pilot symbols and/or TPCsymbols included in the multipath signals F1, F2 and F1+2. The userequipment 300 has a basic configuration of two antennas providing twomultipath signals and one combined multipath signal. Higherconfigurations provide more signals to the SIR estimation unit 310. Forexample, a user equipment having three antennas may provide threemultipath signals F1, F2, F3 and four combined multipath signals F1+2,F1+3, F2+3, F1+2+3 to the SIR estimation unit 310 which then may haveseven SIR estimators.

The power loop controller 320 may include three TPC determinatorsTPC_DET1, TPC_DET2 and TPC_DET1+2 for the basic configuration of twoantennas. Each of the three TPC determinators TPC_DET1, TPC_DET2 andTPC_DET1+2 is coupled to a respective SIR estimator SIR_EST1, SIR_EST2,SIR_EST1+2. The first TCP determinator TPC_DET1 determines a TPC commandTPC1 based on the first SIR value SIR1. The second TCP determinatorTPC_DET2 determines a TPC command TPC2 based on the second SIR valueSIR2. The third TCP determinator TPC_DET1+2 determines a TPC commandTPC1+2 based on the third SIR value SIR1+2. The generated power controlcommands TCP1, TCP2 and TCP1+2 are based on the estimated SIR valuesSIR1, SIR2 and SIR1+2 and are directed to the base station 350 in orderto adjust the power of the downlink signals DL1, DL2. The power loopcontroller 320 includes a switch 321 to switch one of the TPC commandsTPC1, TPC2 and TPC1+2 for transmission to the base station 350 by thetransmitter 360. For higher configurations with three and more antennasa higher number of TPC determinators may be implemented in the powerloop controller 320, e.g. corresponding to the number of SIR estimatorsin the SIR estimation unit 310.

The power loop controller 320 further includes a power adjuster PWR_ADJcoupled to the first 305 and second 306 receiver circuits, and to thecombiner MRC. The power adjuster PWR_ADJ adjusts a power of thetransmitter 360 based on TPC commands included in the multipath signalsF1, F2 or F1+2 transmitted by the base station 350.

In one embodiment, the system can be in three possible states as shownin FIG. 5:

State 1) Antenna 1 301 active, Demod1 and Rake1 305 active. Switch 321is set to select the TPC commands TPC1 for transmission to the basestation 350.State 2) Antenna 2 302 active, Demod2 and Rake2 306 active. Switch 321is set to select the TPC commands TPC2 for transmission to the basestation 350.State 3) Antenna 1 301 and Antenna 2 302 active, Demod1 and Rake1 305and Demod2 and Rake2 306 and Combiner MRC active. Switch 321 is set toselect the TPC commands TPC1+2 for transmission to the base station 350.

Selection of the TPC commands included in the multipath signals F1, F2or F1+2 is performed by the power adjuster PWR_ADJ as follows:

State 1) TPC commands included in multipath signal F1 are used.

State 2) TPC commands included in multipath signal F2 are used.

State 3) TPC commands included in multipath signal F1+2 are used.

The transmitter 360 may transmit an uplink frame UL by means of atransmission antenna 361 to the base station 350. The transmitter 360includes a modulator 363 to modulate an uplink frame 362 including theTPC command TPC_UL switched by the switch 321 and a power unit 364 toamplify the modulated uplink frame 362 to provide the uplink signal ULfor transmission by the transmission antenna 361.

The TPC quality estimator 340 estimates a quality measure of thetransmit power control commands included in the multipath signals F1 andF2 and F1+2. A first quality measure QE1 is based on the first multipathsignal F1, and a second quality measure QE2 is based on the secondmultipath signal F2, and a third quality measure is based on thecombined multipath signal F1+2. The quality measures may besignal-to-noise ratios, signal-to-interference-plus-noise ratios orerror rates of the transmit power control commands.

The diversity controller 330 decides on the state of the system as shownin FIG. 5, hence diversity controller 300 decides on the activation ordeactivation of receiver chains 1 and 2 (a receiver chain includes theantenna, the demodulator and Rake receiver) and of the combiner. Thediversity controller 330 includes a synchronization detector SYNC_DETwhich is coupled to the TPC quality estimator 340 to receive theestimated quality measures QE1 and QE2 and QE1+2. The synchronizationdetector SYNC_DET detects synchronization of the first multipath signalF1 by comparing the first quality measure QE1 against a lower thresholdQ_(out) and against a higher threshold Q_(in). If the first qualitymeasure QE1 falls below the lower threshold Q_(out), the signal F1 isout of synchronization (out-of-sync or OutOfSync). If the first qualitymeasure QE1 exceeds the upper threshold Q_(in), the signal F1 is insynchronization (in-sync or InSync). The synchronization detectorSYNC_DET detects synchronization of the second multipath signal F2 bycomparing the second quality measure QE2 against a lower thresholdQ_(out) and against a higher threshold Q_(in). If the second qualitymeasure QE2 falls below the lower threshold Q_(out), the signal F2 isout of synchronization (out-of-sync or OutOfSync). If the second qualitymeasure QE2 exceeds the upper threshold Q_(in), the signal F2 is insynchronization (in-sync or InSync). The synchronization detectorSYNC_DET detects synchronization of the combined multipath signal F1+2by comparing the quality measure QE1+2 against a lower threshold Q_(out)and against a higher threshold Q_(in). If the quality measure QE1+2falls below the lower threshold Q_(out), the signal F1+2 is out ofsynchronization (out-of-sync or OutOfSync). If the quality measure QE1+2exceeds the upper threshold Q_(in), the signal F1+2 is insynchronization (in-sync or InSync). The lower and higher thresholdsQ_(out) and Q_(in) may be transmitted by the base station 350, e.g. inan initialization phase as configurable parameters or may be stored inthe user equipment 300, e.g. as pre-configured parameters.

The synchronization detector SYNC_DET provides a synchronization signal331 at its output depending on the synchronization of one of themultipath signals F1 and F2 and F1+2. The synchronization signal 331depends on the system state. In State 1) the synchronization signal 331may indicate out-of-sync if the multipath signal F1 is out ofsynchronization, and may indicate in-sync if the multipath signal F1 isin synchronization. In State 2) the synchronization signal 331 mayindicate out-of-sync if the multipath signal F2 is out ofsynchronization, and may indicate in-sync if the multipath signal F2 isin synchronization. In State 3), the synchronization signal 331 mayindicate out-of-sync if the multipath signal F1+2 is out ofsynchronization, and may indicate in-sync if the multipath signal F1+2is in synchronization. Depending on the synchronization signal 331 thetransmitter 360 may be turned on or off. If the synchronization signal331 indicates out-of-sync, the transmitter 360 may be turned off inorder to avoid the transmitter 360 from transmitting uplink signals ULbased on unsecure detected transmit power control commands in thedownlink signals DL1, DL2 or DL1+2. If the synchronization signal 331indicates in-sync, the transmitter 360 may be turned on due to areliable detection of transmit power control commands in the downlinksignals DL1, DL2 or DL1+2.

Depending on the synchronization signal 331 provided at the output ofthe synchronization detector SYNC_DET the plurality of receiver circuits305, 306 may be switched on. If the synchronization signal 331 indicatesthe out-of-sync state in State 1 or State 2, both receiver circuits 305,306 may be switched on to increase receiver diversity in order toimprove the receiver gain of the user equipment 300, hence a statetransition to State 3 is performed.

The diversity controller 330 further includes a high-windup detectorHW_DET which receives the estimated SIR values SIR1 and SIR2 of thefirst and second SIR estimators SIR_EST1 and SIR_EST2. In State 1, theestimated SIR value SIR_EST1 is compared against a target SIR(SIR_(target)) to check if the received downlink signal DL1 is in ahigh-windup state which will be explained below (see FIG. 7). In State2, the estimated SIR value SIR_EST2 is compared against a target SIR(SIR_(target)) to check if the received downlink signal DL2 is in ahigh-windup state. In case of DPCH, the target SIR may be determinedfrom a target block error rate which may be determined from a targetQuality of Service QoS_(target). The target Quality of Service may betransmitted by the base station 350, e.g. in an initialization phase asa configurable parameter or may be stored in the user equipment 300,e.g. as a pre-configured parameter. In case of F-DPCH, the target SIRmay be determined from a target TPC command error rate.

Depending on the state signaled at the output of the high-windupdetector HW_DET the plurality of receiver circuits 305, 306 may beswitched on or off. In State 1 or State 2, if the output of thehigh-windup detector HW_DET indicates a high-windup state, both receivercircuits 305, 306 may be switched on to increase receiver diversity inorder to improve the receiver gain of the user equipment 300, hence astate transition to State 3 is performed.

For state transitions from State 3 back to State 1 or State 2, a timermay be started when entering State 3. When the timer expires, statetransition to State 1 or State 2 may be performed. The receiver circuitwhich stays switched-on (i.e., state transition to State 1 or State 2)may be the receiver circuit providing the downlink signal having thebetter SIR or the better TPC quality. Alternatively, the diversitycontroller may check other measurements performed by the user equipment(e.g. CPICH Ec/Io or CPICH RSCP as defined by 3GPP) in order to decidewhen to return to State 1 or State 2.

The diversity controller 330 may include a combiner COMB, which iscoupled to the synchronization detector SYNC_DET and the high-windupdetector HW_DET. The combiner COMB combines the synchronization signal331 and the output signal of the high-windup detector HW_DET accordingto a specified rule and provides an output signal indicating a state ofreduced performance as a combination of an out-of-sync state and ahigh-windup state. The specified rule of the combiner COMB may be alogical AND combination or a logical OR combination or any other kind ofcombination. If the output of the combiner COMB indicates a state ofreduced performance, both receiver circuits 305, 306 may be switched onto increase receiver diversity in order to improve the performance ofthe user equipment 300.

There may be three embodiments of the diversity controller 330 in theuser equipment 300 described above. In a first embodiment the diversitycontroller 330 includes the synchronization detector SYNC_DET to providethe out-of-sync and in-sync states for controlling the receiver circuits305, 306. The high-windup detector HW_DET and the combiner COMB are notneeded.

In a second embodiment the diversity controller 330 includes thehigh-windup detector HW_DET to provide the high-windup and nonhigh-windup states for controlling the receiver circuits 305, 306. Thesynchronization detector SYNC_DET is not needed for controlling thereceiver circuits 305, 306 but may be needed for switching on and/or offthe transmitter 360. The combiner COMB is not needed.

In a third embodiment the diversity controller 330 includes thesynchronization detector SYNC_DET, the high-windup detector HW_DET andthe combiner COMB to provide the states of reduced and non-reducedperformance for controlling the receiver circuits 305, 306. Thesynchronization detector SYNC_DET may be additionally used for switchingon and/or off the transmitter 360.

The base station 350 includes a receive antenna 352 to receive theuplink signal UL from the user equipment 300 and a demodulator todemodulate the received uplink signal UL providing a received uplinkframe 358. Depending on a transmit power control command TPC_UL includedin the received uplink frame 358 the base station 350 adjusts its powerfor transmitting downlink signals DL1, DL2. The downlink signals DL1,DL2 are generated from downlink frames 354 including downlink transmitpower control commands TPC_DL which are used by the base station 350 torequest the user equipment 300 adjusting a power of the uplink signalsUL transmitted by the user equipment 300. The base station 350 furtherincludes a power range adjuster 355 to adjust a power range of thedownlink frames 354 between a minimum power P_MIN and a maximum powerP_MAX. Both power values are configurable by the network. If uplinktransmit power control commands TPC_UL request a higher power than themaximum power P_MAX configured by the network, the power of the downlinksignals DL1, DL2 is limited by the power range adjuster 355 to themaximum power P_MAX (high-windup scenario). A modulator 356 modulatesthe downlink frames 354 to analog downlink signals DL1, DL2 transmittedby the transmission antenna 351 to the user equipment 300.

FIG. 4 schematically illustrates examples of downlink signals and uplinksignals between a base station and a user equipment according to oneembodiment. The embodiment is according to 3GPP TS 25.214 V7.15.0(2010-03), Figure B.1. A first frame 401, e.g. a Downlink DPCCH frame,including data fields (Data1, Data2), pilot symbols (PILOT), transmitpower control commands (TPC) and Transport Format Combination Indicator(TFCI) bits may correspond to the downlink frame 354 of the base station350 depicted in FIG. 3, including downlink power control commands TPC_DLwhich are used by the base station 350 to request the user equipment 300adjusting a power of the uplink signals UL transmitted by the userequipment 300.

A second frame 402 may correspond to the detected multipath signals F1,F2 or the combined multipath signal F1+2, which are received by the userequipment 300 after a propagation delay and depending on multipathdiversity. The content of the second frame 402 corresponds to thecontent of the first frame 401. However, the second frame 402 is delayedby a propagation delay, which depends on the respective multipath beingused for transmission.

A third frame 403, e.g. an Uplink DPCCH frame, including transmit powercontrol commands (TPC), pilot symbols (PILOT) and TFCI bits maycorrespond to the uplink frame 362 of the user equipment 300 depicted inFIG. 3, which includes uplink transmit power control commands TPC_UL.The TPC commands of the third frame 403 may be determined by an SIRmeasurement of pilot symbols or TPC symbols of the second frame 402, F1,F2, F1+2.

A fourth frame 404 may correspond to the received uplink frame 358 ofthe base station 350 depicted in FIG. 3. The fourth frame 404 is delayedby the propagation delay in uplink direction, which depends on themultipath fading. The base station may determine the downlink transmitpower control commands TPC_DL based on an SIR measurement of the pilotsymbols of the uplink frame 404, 358 and insert TPC_DL into the downlinkframe 401, 354.

FIG. 6 schematically illustrates a user equipment 600 according to oneembodiment. The user equipment 600 includes a plurality of antennas,e.g. a first antenna 601 and a second antenna 602, to receive downlinksignals from a base station. The user equipment 600 includes a pluralityof radio frequency (RF) units 603, 604 (RF₁, RF₂), each of them coupledto a respective antenna 601, 602 for mixing and demodulating thereceived downlink signals.

The user equipment 600 includes a receiver 608, e.g. a type 1 receiver,including a plurality of rake receiver circuits 605, 606 and a combiner607, e.g. a maximum ratio combiner MRC. Although FIG. 6 depicts only tworake receiver circuits 605 and 606, the receiver 608 may include anyother number of rake receiver circuits, e.g. three, four or more. Eachof the rake receiver circuits is coupled to a respective one of theplurality of RF units 603, 604. For example, the first rake receivercircuit 605 may be coupled to the first RF unit 603 and the second rakereceiver circuit 606 may be coupled to the second RF unit 604. FIG. 6illustrates a number of two antennas with corresponding RF units andrake receiver circuits. Any other number is likewise possible.

The user equipment 600 further includes an SIR estimation unit 610including a plurality of SIR estimators 611, 612, 613, a switch 621, apower loop controller 620 and a diversity controller 630. Each of theSIR estimators 611, 612, 613 are coupled to a respective one of theplurality of rake receiver circuits 605, 606 and to the combiner 607.The switch 621 is coupled to the power loop controller 620 and to thediversity controller 630.

The functionality of the RF units 603, 604, the rake receiver circuits605, 606, the combiner 607 may correspond to the respective circuitsdescribed above in connection with FIG. 3. The functionality of the SIRestimation unit 610 may correspond to the functionality of the SIRestimation unit 310 described above in connection with FIG. 3. The SIRestimators 611, 612, 613 may estimate asignal-to-interference-plus-noise ratio value, a signal-to-interferenceratio value, a signal-to-noise ratio value or any other quality measurecharacterizing the received multipath signal at the respective output ofthe receiver 608.

The power loop controller 620 of FIG. 6 is directly connected to each ofthe SIR estimators 611, 612, 613 to receive all (or at least more thanone) SIR values provided by the SIR estimators 611, 612, 613. The powerloop controller 620 contains a first TPC determinator (TPC_Ant1), asecond TPC determinator (TPC_Ant2) and a third TPC determinator (TPC).Each of the TPC determinators is coupled to a respective one of the SIRestimators 611, 612, 613 to receive the respective SIR values. For eachof the received SIR values the power loop controller 620, i.e. the TPCdeterminators of the power loop controller 620, may determine arespective TPC command based on the respective SIR value. The TPCdeterminators may be configured to estimate TPC symbols included in thedownlink signals as a measure for the quality of the received downlinksignals. The SIR estimators 611, 612, 613 may be configured to estimateSIR values of pilot symbols included in the downlink signals as ameasure for the quality of the received downlink signals. The power loopcontroller 620 performs Downlink Power Control (DLPC) processing byproviding transmit power control (TPC) commands 622 which may be sentback to the network (NW), e.g. by a transmitter 360 as depicted in FIG.3. The generation of TPC commands may be based on the SIR valuesestimated by the SIR estimators 611, 612, 613.

The switch 621 is controlled by the diversity controller 630 and selectsa respective TPC command determined by the TPC determinators of thepower loop controller 620. The setting of the switch 621 depends on thesystem state determined by the diversity controller 630. The uplink (UL)TPC commands may be sent back to the network (NW). FIG. 6 illustrates aselection of TPC commands by the switch 621.

Beside the selection of TPC commands the diversity controller 630 mayfurther control activation and/or deactivation of the rake receivercircuits 605, 606 by activating those rake receiver circuits receivingthe multipath signals of highest signal-to-interference-plus-noiseratios and deactivating those rake receiver circuits receiving multipathsignals having worse quality. For example in a configuration with fiveantennas and five rake receiver circuits, the diversity controller 630may activate the two rake receiver circuits providing the highest SIRvalues and deactivate the three rake receiver circuits providing thelowest SIR values. The RxDiv processing makes the user equipment reduceits power consumption and improve its accuracy, as rake receivercircuits providing distorted signals can be switched off. Switching offdistortion results in a higher accuracy because only signals having highsignal-to-interference-plus-noise ratios are used for furtherprocessing. The switch may further control activation/deactivation ofthe combiner 607, the RF units 603, 604 and the antennas 601, 602.

The idea behind this concept is to turn on receiver diversity (RxDiv)only when the performance improvement achieved via RxDiv is actuallyrequired in order to avoid call drops. Although the resulting device maynot be fully compliant to the 3GPP “Enhanced Performance RequirementsType 1” Specification as described in the document 3GPP TS25.101 V7.16.0(2009-05), Sections 8.3, 8.6 and 8.8, however, it will achievesignificantly reduced call drop rates at comparatively small increase ofcurrent consumption and hence, at only slightly reduced talk time.

FIG. 7 schematically illustrates a performance diagram of a userequipment according to one embodiment depicting a high-windup scenario.In the field, downlink channels, e.g. DPCH channels, are operated by thenetwork (NW), i.e. the base station, with closed loop power control,i.e. a quality of service (QoS) target may be set by the network as ablock error rate and outer and inner loop power control mechanism may beapplied to guarantee, e.g. by requesting additional transmit power fromthe network in case it is needed, that the QoS target is actuallyachieved. Nevertheless, call drops may occur in some situations.

One such situation is when the network downlink (e.g. DPCH or F-DPCH)transmit power reaches the upper limit set by the network. This scenariois illustrated in FIG. 3. The user equipment 300 requests the basestation 350 by the TPC_UL command in the uplink frame 358 to increasethe power of the downlink frames DL1, DL2. Such an increase, however,conflicts with the maximum power value P_MAX of the power range adjuster355 which maximum power is set by the network. The base station 350 isnot allowed to increase the power beyond the admissible level. The powercontrol mechanism is no longer able to guarantee the QoS target andtransmission errors may occur, which may lead finally to a call drop.This scenario is referred to as the power control high-windup situationand is illustrated in FIG. 7.

FIG. 7 exemplarily depicts the measured SIR value with respect to thetarget SIR value. As long as the network is able to provide the powerthe user equipment requests, the closed power loop mechanism controlsthe power of the downlink signals to be as high as needed to make themeasured SIR track the target SIR. At about two thirds of the time axisthe maximum power is limited by the base station such that the available(measured) SIR at the user equipment becomes significantly smaller thanthe required (target) SIR at the user equipment. The user equipment isin a high-windup state. Depending on the duration of the high-windupstate and depending on the difference between target SIR and measuredSIR the user equipment may become unable to hold the communication, acall drop will finally happen.

User equipments according to embodiments depicted in FIGS. 1-3, 5 and 6may be able to detect the high-windup situation, e.g. by measuring andfiltering the difference between target SIR and measured SIR. Thehigh-windup state may be detected when a difference between measured SIRat the user equipment and target SIR at the user equipment exceeds athreshold. When entering (or even before entering) a high-windupsituation, such user equipments may activate receiver diversity (RxDiv),providing considerable performance gain. Since the required transmitpower is accordingly lower when RxDiv is turned on, the measured SIR mayreach the target SIR and the high-windup situation may be left oravoided. At least the RxDiv performance gain for user equipmentsaccording to embodiments of FIGS. 1-3 and 6 significantly reducesoccurrences of high-windup states and thus the probability of calldrops.

RxDiv may be smoothly deactivated by introducing new states into thesystem state diagram as shown in FIG. 13. The state diagram shown inFIG. 5 with States 1, 2, 3 is extended by the new States 3 a and 3 b (socalled DLPC trial states):

State 3 a) Antenna 1 301 and Antenna 2 302 active, Demod1 and Rake1 305and Demod2 and Rake2 306 and Combiner MRC active. Switch 321 is set toselect the TPC commands TPC1 for transmission to the base station 350.

State 3 b) Antenna 1 301 and Antenna 2 302 active, Demod1 and Rake1 305and Demod2 and Rake2 306 and Combiner MRC active. Switch 321 is set toselect the TPC commands TPC2 for transmission to the base station 350.

In the new States 3 a and 3 b, RxDiversity is kept turned on (bothreceiver chains are kept active) and only the downlink power control(DLPC) is switched to consider only one antenna (Antenna 1 in State 3 aand Antenna 2 in State 3 b).This allows to keep RxDiv switched on and thus maintain demodulationperformance and switch only the DLPC to one antenna in order to checkwhether a windup situation still exists or not, before returning toState 1 or State 2. The one antenna used for DLPC (hence, the statetransition to State 3 a or 3 b) may be the antenna showing better signalquality. The SNR estimation unit 610 uses a plurality of SNR estimators611, 612, 613. One SNR estimator 613 is used for operation with twoantennas 601, 602 and the other SNR estimators 611, 612 are used foroperation with only one of the antennas 601, 602. Thereby, it can easilybe detected in States 3 a and 3 b if the high-windup state stillcontinues without compromising the diversity gain, as both antennas arestill active and receiving. If high-windup still exists, RxDiv is keptturned on, hence a state transition back to State 3 is performed.Otherwise, a state transition from State 3 a to State 1 or from State 3b to State 2 is performed (i.e. the worse antenna (and/or thecorresponding receiver circuit) is turned off).

The basic concept of such user equipments is to turn on RxDiv only whenthe performance improvement achieved via RxDiv is actually required inorder to avoid call drops. Thereby, nearly the same reduction in calldrop rates will be achieved as when RxDiv is always turned on duringdownlink (e.g. DPCH) reception, but at significantly reduced currentconsumption. Hence, the talk-time of such user equipments using RxDivcontrol will be significantly larger than for a device using RxDiv allthe time during downlink (e.g. DPCH) reception, and there will only be arelatively small reduction in talk-time compared to a device using noRxDiv at all.

The high-windup determination may be realized by a diversity controller,e.g. a diversity controller 330 as depicted in FIG. 3 which includes ahigh-windup detector HW_DET receiving estimated SIR values SIR1 and SIR2of two multipath signals provided by an SIR estimation unit 310. Thevalue SIR_(target) of FIG. 3 may correspond to the target SIR of FIG. 7.The diversity controller may accordingly turn off/on the receivercircuits.

FIG. 8 schematically illustrates a performance diagram of a userequipment according to one embodiment depicting an out-of-sync scenario.Synchronization states of the user equipment, i.e. in-sync andout-of-sync states are characterized by a quality of transmit powercontrol (TPC) commands transmitted in the downlink signals from basestation to user equipment. When this quality falls below a lowerthreshold (OutofSync threshold in FIG. 8) the user equipment is unableto reliably detect the received TPC commands and falls out ofsynchronization, i.e. is in the out-of-sync state. When said qualityexceeds an upper threshold (InSync threshold in FIG. 8) the userequipment is able to reliably detect the received TPC commands and toadjust the power of its transmitter, the user equipment is in thein-sync state.

According to one embodiment, user equipments may measure the quality ofthe TPC commands as the SIR value of the TPC commands, referred to asRhoTPC in FIG. 8. User equipments may also use another quality measure,such as the SNR value or an error value of the TPC commands. When thequality of received TPC commands, e.g. measured as the RhoTPC value,hits the OutOfSync threshold depicted in FIG. 8 link synchronization hasto be maintained and verified during ongoing calls according to 3GPPusing the quality of the TPC commands steering the transmit power of theuser equipment. When the actual RhoTPC hits the OutOfSync threshold, theuser equipment transmitter must be turned off according to 3GPP, and maybe turned on again only when another quality threshold, the so calledInSync threshold which is higher than the OutOfSync threshold, is metagain. If this is not achieved within a certain time specified by thenetwork, a call drop cannot be avoided. This scenario is referred to asthe out-of-sync situation and is illustrated in FIG. 8.

FIG. 8 exemplarily depicts the RhoTPC value with respect to the InSyncand OutOfSync thresholds. As long as the quality of the TPC commands,i.e. RhoTPC is above the lower OutOfSync threshold, the user equipmentis in in-sync state and the TPC commands sent by the base station can bereliably detected by the user equipment. At about two thirds of the timeaxis the RhoTPC value falls below the OutOfSync threshold. The userequipment enters the out-of-sync state and turns off its transmitter.Depending on the duration of the out-of-sync state the user equipmentmay become unable to hold the communication provoking a call drop.

User equipments according to embodiments depicted in FIGS. 1-3, 5 and 6may be able to detect the out-of-sync situation, e.g. by measuring theRhoTPC value and comparing it to the lower OutOfSync threshold. Theout-of-sync scenario can be easily detected by measuring and filteringthe difference between OutOfSync threshold and measured RhoTPC. Whenentering an out-of-sync situation, such user equipments may activatereceiver diversity (RxDiv), providing considerable performance gain.Since the required transmit power and thus the power of the TPC commandsin the downlink signals and its RhoTPC value is accordingly lower whenRxDiv is turned on, the RhoTPC value may reach the InSync threshold andthe out-of-sync situation may be finished. At least the RxDivperformance gain for user equipments according to embodiments of FIGS.1-3, 5 and 6 significantly reduces occurrences of out-of-sync states andthus the probability of call drops.

For turning RxDiv off the user equipment may use the procedures asdescribed above in [0073] and [0095].

The user equipment may turn RxDiv on if either a high-windup conditionor an out-of-sync condition or both high-windup and out-of-syncconditions are fulfilled. Duration of RxDiv utilization may bedetermined by a timer so that RxDiv is switched off after a certain timelimit. The timer itself may be started if either a high-windup conditionor an out-of-sync condition or both high-windup and out-of-syncconditions are fulfilled. Hence, when the timer expires, a statetransition from State 3, 3 a or 3 b to State 1 or State 2 may beperformed.

If RhoTPC estimators are not available, the procedure described above inconnection with FIG. 7 and the high-windup situation can be used. Thisis possible since out-of-sync state is usually accompanied byhigh-windup state and vice versa.

The out-of-sync determination may be realized by a diversity controller,e.g. a diversity controller 330 as depicted in FIG. 3 which includes asynchronization detector SYNC_DET receiving estimated quality measuresQE1 and QE2 of two multipath signals provided by a TPC quality estimator340. Upper and lower threshold Q_(in) and Q_(out) of FIG. 3 maycorrespond to upper InSync threshold and lower OutOfSync threshold ofFIG. 8. The diversity controller may accordingly turn off/on thereceiver circuits.

FIG. 9 schematically illustrates a test case for an out-of-sync scenarioin a user equipment according to one embodiment. The test case isaccording to 3GPP TS 34.121-1 V8.9.0 (2009-12), Section 5.4.4“Out-of-synchronisation handling of output power”. Both antennaconnectors of the device under test, e.g. the user equipment accordingto an embodiment depicted in FIGS. 1-3, 5 and 6, shall be connected. TheAWGN (additional white gaussian noise) signals applied to each receiverantenna connector shall be uncorrelated. The levels of the test signalapplied to each of the antenna connectors shall be as defined in section5.5.5.2.

In this test case, the requirements for the user equipment are that:

-   -   1. The user equipment shall not shut its transmitter off before        point B,    -   2. The user equipment shall shut its transmitter off before        point C, which is T_(off)=200 ms after point B,    -   3. The user equipment shall not turn its transmitter on between        points C and E,    -   4. The user equipment shall turn its transmitter on before point        F, which is T_(on)=200 ms after point E.

While a user equipment with static RxDiv according to 3GPP has RxDivactivated at all times during the test and hence shows the same level ofcurrent consumption throughout the test, a user equipment according toembodiments depicted in FIGS. 1-3, 5 and 6 will switch RxDiv on onlyafter reaching point B. A short time interval δ_(ON) after point B theuser equipment will detect out-of-sync state and turns RxDiv on whichcauses an increase in power consumption up to the level P_(RXDivON,UE).Similarly a short time interval δ_(OFF) after point E the user equipmentwill detect in-sync state and turns RxDiv off causing a decrease incurrent consumption down to the level P_(RXDivOFF,UE).

FIG. 10 schematically illustrates a test case for a high-windup scenarioin a user equipment according to one embodiment. The test case isaccording to 3GPP TS 34.121-1 V8.9.0 (2009-12), Section 7.8.3A “Powercontrol in the downlink, wind up effects”. In this test, the deviceunder test, e.g. the user equipment according to an embodiment depictedin FIGS. 1-3, 5 and 6, is forced into a high-windup scenario in stage 2of the test by switching the maximum available power of the base stationfrom a high level P_(MAX,BS) in stage 1 to a low level P_(MIN,BS) instage 2. In stage 3 the maximum available power is switched back to thehigh level P_(MAX,BS) forcing the user equipment to leave thehigh-windup state.

While a user equipment with static RxDiv according to 3GPP will use bothreceive antennas throughout the test, i.e. RxDiv is activated at alltimes during the test, and hence shows the same level of currentconsumption throughout the test, a user equipment according toembodiments depicted in FIGS. 1-3, 5 and 6 will switch RxDiv on onlyafter detecting high-windup in stage 2 of the test. A short timeinterval ON after reaching stage 2 the user equipment will detecthigh-windup state and turn RxDiv on causing a significant increase inpower consumption up to the level P_(RXDivON,UE). Similarly, a shorttime interval δ_(OFF) after leaving stage 2 the user equipment willdetect that high-windup state is over and turn RxDiv off causing asignificant decrease in current consumption down to the levelP_(RXDivOFF,UE).

FIG. 11 schematically illustrates a performance gain diagram of a userequipment according to one embodiment. The diagram depicts twoperformance curves of a user equipment according to an embodimentdepicted in FIGS. 1-3 and 6 which is tested according to the test 5a of3GPP TS 25.101 V7.16.0 (2009-05), Section 8.3.1 in a multipath fadingpropagation (VA30) for supporting the enhanced performance requirementstype 1 for DCH. When the user equipment has RxDiv turned on (leftcurve), the base station may reduce its transmission power DPCH Ec/Iorby 3 to 5 dB compared to the user equipment state with RxDiv turned off(right curve). The performance gain of RxDiv depends on the requiredblock error rate (BLER). When a high block error rate of 5% (upperpoints of left and right curve) is tolerated by the networkadministrator, a gain of 3 dB may be reached with receiver diversityturned on. When a low block error rate of 0.2% (lower points of left andright curve) is required by the network administrator, a gain of 5 dBmay be reached with receiver diversity turned on.

It may be provided that the user equipment turns RxDiv on only when theperformance improvement achieved by means of RxDiv is actually requiredin order to avoid call drops. Thereby, the gain of 3-5 dB as shown inFIG. 11 and nearly the same reduction in call drop rates may be achievedcompared to a user equipment with static receiver diversity, but atsignificantly reduced current consumption.

FIG. 12 schematically illustrates a performance diagram of a userequipment according to one of the embodiments illustrated in FIGS. 1 to3 and 6. The diagram depicts three curves illustratingsignal-to-interference-plus-noise ratios (SIRs). The three curves depictSIR target which is set by the outer loop power control in case of DPCHtransmission based on the QoS target (target block error rate) set bythe network, or set according to the target TPC command error rate setby the network in case of F-DPCH, SIR which corresponds to measured SIRand describes the signal-to-interference-plus-noise ratio measured atthe user equipment and true SIR which is measured in a trial state todescribe the available SIR when the full RxDiv gain is available.

FIG. 12 illustrates six stages on the time axis. In a first stagereceiver diversity (RxDiv) is switched off (i.e. one of the two antennasand the corresponding RF and receiver circuits are switched off) andpower control (PC) is applied using the active antenna only. The systemis in State 1 or 2 as shown in FIG. 13. According to FIG. 6, forexample, the RxDiv controller 630 controls the switch 621 to switch oneof the inputs of the switch 621 to its output in order to send a TPCcommand 622 (TPC Ant1 or TPC Ant2) related to one of the antennas 601,602 back to the network. For example, TPC command TPC Ant1 related tothe first antenna 601 is selected. At the end of stage 1 a windupsituation occurs, e.g. multipath fading occurs which decreases the SIRof the multipath signal received by the first antenna 601, while thenetwork is not able to increase its power.

When the windup situation is detected by the user equipment, thediversity controller activates RxDiv (i.e. the user equipment activatesboth antennas, both RF and receiver circuits) and performs power controlon both antennas in stage 2. Hence the diversity controller performs astate transition to system State 3. A higher antenna gain resulting fromRxDiv activation makes the measured SIR converge to the SIR Target. OnceRxDiv is started, trials are performed periodically, e.g. at stage 3 andstage 5 (the diversity controller performs state transitions to DLPCtrial States 3 a or 3 b), to turn it off again. The duration of theStates 3, 3 a and 3 b may be determined by using individual timers.

At stage 3 power control is performed on the antenna obtaining betterresults (DLPC trial state 3 a or 3 b) while RxDiv is kept on and awindup situation still occurs. Therefore, a state transition back toState 3 is performed, hence at stage 4 power control is again performedon both antennas. Here the measured SIR converges to target SIR. Atstage 5 power control is again performed on the better antenna (DLPCtrial state 3 a or 3 b), while RxDiv is kept on and, initially thewindup situation still occurs. But then the windup situation hasfinished and this is detected by the user equipment such that a statetransition to system State 1 or 2 is performed in stage 6, i.e. thereceiver chain (antenna, RF and receiver) showing worse performance isswitched off and power control and reception are performed on the betterantenna. Both at stage 1 (before the occurrence of the windup situation)and stage 6 (after the occurrence of the windup situation), RxDiv isswitched off and the user equipment is in a power saving mode.

In FIG. 12 RxDiv is kept on at stages 2-5 and power control is performedin stage 3 and stage 5 for the better antenna only. It can be easilyevaluated whether the windup situation still exists with the betterantenna or not. RxDiv is only turned off after a verification thatwindup situation does no longer exist with the better antenna.

A method for downlink power control (DLPC) of a user equipment includinga plurality of antennas and a plurality of receiver circuits eachcoupled to a respective one of the plurality of antennas is presented.The method includes receiving downlink signals from a base station bythe plurality of antennas, processing the received downlink signals bythe plurality of receiver circuits, estimating a quality of the receiveddownlink signals, selectively activating at least one of the receivercircuits depending on the estimated quality of the received downlinksignals and generating transmit power control commands based on theestimated quality of the received downlink signals. The transmit powercontrol commands are directed to the base station to adjust the power ofthe downlink signals. The quality of the received downlink signals maybe estimated by estimating SIR values of pilot symbols and/or TPCsymbols included in the downlink signals.

A method for uplink power control (ULPC) of a user equipment including aplurality of antennas and a plurality of receiver circuits each coupledto a respective one of the plurality of antennas is presented. Themethod includes receiving downlink signals from a base station by theplurality of antennas, processing the received downlink signals by theplurality of receiver circuits, estimating a quality measure of transmitpower control commands included in the downlink signals, selectivelyactivating at least one of the receiver circuits depending on theestimated quality measure and adjusting the power of uplink signalsdirected to the base station based on the transmit power controlcommands. The power of the uplink signals may be turned off if thequality measure falls below a first threshold value and may be turned onif the quality measure exceeds a second threshold value.

In addition, while a particular feature or aspect of an embodiment ofthe invention may have been disclosed with respect to only one ofseveral implementations, such feature or aspect may be combined with oneor more other features or aspects of the other implementations as may bedesired and advantageous for any given or particular application.Furthermore, to the extent that the terms “include”, “have”, “with”, orother variants thereof are used in either the detailed description orthe claims, such terms are intended to be inclusive in a manner similarto the term “comprise”. Furthermore, it should be understood thatembodiments of the invention may be implemented in discrete circuits,partially integrated circuits or fully integrated circuits orprogramming means. Also, the terms “exemplary”, “for example” and “e.g.”are merely meant as an example, rather than the best or optimal. It isalso to be appreciated that features and/or elements depicted herein areillustrated with particular dimensions relative to one another forpurposes of simplicity and ease of understanding, and that actualdimensions may differ substantially from that illustrated herein.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. For instance,implementations described in the context of a user equipment could beapplied to WCDMA transceivers, UMTS transceivers or to mobilecommunication transceivers relating to other technical standards such ase.g. GSM or derivatives thereof or applying other multiple accessschemes such as e.g. TDMA, FDMA etc. This application is intended tocover any adaptations or variations of the specific embodimentsdiscussed herein. Therefore, it is intended that this invention belimited only by the claims and the equivalents thereof.

What is claimed is:
 1. A circuit, comprising: a quality estimation unitconfigured to estimate a quality of downlink signals, wherein each ofthe downlink signals is derived from a respective one of a plurality ofantenna ports, wherein the quality estimation unit comprises asignal-to-interference-and-noise ratio (SIR) estimation unit configuredto estimate SIR values of transmission power control (TPC) symbols or ofpilot symbols and TPC symbols comprised in the downlink signals as thequality of the downlink signals; a power loop controller configured togenerate transmit power control commands based on the estimated qualityof the downlink signals, the transmit power control commands configuredto request an adjustment of a power of the downlink signals; and adiversity controller configured to selectively activate and deactivateone or more of a plurality of receiver circuits each coupled to arespective one of the plurality of antenna ports.
 2. The circuit ofclaim 1, further comprising a transmitter configured to transmit uplinksignals, the uplink signals comprising the transmit power controlcommands.
 3. The circuit of claim 1, wherein the quality estimation unitcomprises a plurality of SIR estimators, and wherein each of thereceiver circuits is coupled to a respective one of the plurality of SIRestimators.
 4. The circuit of claim 3, further comprising a combinercircuit coupled to at least two receiver circuits of the plurality ofreceiver circuits, the combiner circuit being coupled to one of theplurality of SIR estimators.
 5. The circuit of claim 3, wherein thepower loop controller comprises a plurality of TPC determinators,wherein each of the TPC determinators is coupled to a respective one ofthe plurality of SIR estimators.
 6. The circuit of claim 5, wherein eachof the plurality of TPC determinators is configured to determine atransmit power control command based on the SIR value estimated by theSIR estimator coupled to the respective TPC determinator.
 7. A circuit,comprising: a quality estimation unit configured to estimate a qualityof downlink signals, wherein each of the downlink signals is derivedfrom a respective one of a plurality of antenna ports, wherein thequality estimation unit comprises a plurality of SIR estimators, andwherein each one of a plurality of receiver circuits is coupled to arespective one of the plurality of antenna ports and to a respective oneof the plurality of SIR estimators; a power loop controller configuredto generate transmit power control commands based on the estimatedquality of the downlink signals, the transmit power control commandsconfigured to request an adjustment of a power of the downlink signals,wherein the power loop controller comprises a plurality of TPCdeterminators, wherein each of the TPC determinators is coupled to arespective one of the plurality of SIR estimators, wherein each of theplurality of TPC determinators is configured to determine a transmitpower control command based on the SIR value estimated by the SIRestimator coupled to the respective TPC determinator; a diversitycontroller configured to selectively activate and deactivate one or moreof the receiver circuits; and a switch coupled between the plurality ofTPC determinators and the transmitter and configured to transfer atleast one of the transmit power control commands determined by therespective TPC determinator to the transmitter.
 8. The circuit of claim7, wherein the switch is controlled by the diversity controller.
 9. Thecircuit of claim 1, wherein the diversity controller is configured todetect a high-windup situation or an out-of-sync situation, or both. 10.A circuit, comprising: a quality estimation unit configured to estimatea quality of downlink signals, wherein each of the downlink signals isderived from a respective one of a plurality of antenna ports; a powerloop controller configured to generate transmit power control commandsbased on the estimated quality of the downlink signals, the transmitpower control commands configured to request an adjustment of a power ofthe downlink signals; and a diversity controller configured toselectively activate and deactivate one or more of a plurality ofreceiver circuits each coupled to a respective one of the plurality ofantenna ports, wherein the diversity controller is configured to detecta high-windup situation or an out-of-sync situation, or both, andwherein the diversity controller is configured to activate at least oneof the receiver circuits upon detecting a start of the high-windup orout-of-sync situation.
 11. The circuit of claim 10, wherein thediversity controller is configured to deactivate at least one of theactivated receiver circuits upon detecting an end of the high-windup orout-of-sync situation.
 12. A circuit, comprising: a quality estimationunit configured to estimate a quality of downlink signals, wherein eachof the downlink signals is derived from a respective one of a pluralityof antenna ports; a power loop controller configured to generatetransmit power control commands based on the estimated quality of thedownlink signals, the transmit power control commands configured torequest an adjustment of a power of the downlink signals; and adiversity controller configured to selectively activate and deactivateone or more of a plurality of receiver circuits each coupled to arespective one of the plurality of antenna ports, wherein the diversitycontroller is configured to detect a high-windup situation or anout-of-sync situation, or both, and wherein the diversity controller isconfigured to detect a start of the high-windup situation by comparing adifference between the SIR values and target SIR values against athreshold.
 13. A circuit, comprising: a quality estimation unitconfigured to estimate a quality of downlink signals, wherein each ofthe downlink signals is derived from a respective one of a plurality ofantenna ports; a power loop controller configured to generate transmitpower control commands based on the estimated quality of the downlinksignals, the transmit power control commands configured to request anadjustment of a power of the downlink signals; and a diversitycontroller configured to selectively activate and deactivate one or moreof a plurality of receiver circuits each coupled to a respective one ofthe plurality of antenna ports, wherein the diversity controller isconfigured to detect a high-windup situation or an out-of-syncsituation, or both, and wherein the diversity controller is configuredto detect a start of the out-of-sync situation by comparing a qualitymeasure based on transmit power control commands against a threshold.14. A circuit, comprising: a quality estimation unit configured toestimate a quality of downlink signals, wherein each of the downlinksignals is derived from a respective one of a plurality of antennaports; a power loop controller configured to generate transmit powercontrol commands based on the estimated quality of the downlink signals,the transmit power control commands configured to request an adjustmentof a power of the downlink signals; and a diversity controllerconfigured to selectively activate and deactivate one or more of aplurality of receiver circuits each coupled to a respective one of theplurality of antenna ports, wherein the diversity controller isconfigured to detect a high-windup situation or an out-of-syncsituation, or both, wherein the diversity controller comprises a firsttimer which is started upon detection of a start of the high-windup orthe out-of-sync situation, and wherein the diversity controller detectsan end of the high-windup or the out-of-sync situation when the firsttimer expires.
 15. A circuit, comprising: a quality estimation unitconfigured to estimate a quality of downlink signals, wherein each ofthe downlink signals is derived from a respective one of a plurality ofantenna ports; a power loop controller configured to generate transmitpower control commands based on the estimated quality of the downlinksignals, the transmit power control commands configured to request anadjustment of a power of the downlink signals; and a diversitycontroller configured to selectively activate and deactivate one or moreof a plurality of receiver circuits each coupled to a respective one ofthe plurality of antenna ports, wherein the diversity controller isconfigured to detect a high-windup situation or an out-of-syncsituation, or both, wherein the diversity controller is configured toswitch during a high-windup or an out-of-sync situation between a firststate and a second state, wherein in the first state the power loopcontroller is configured to generate the transmit power control commandsbased on SIR values of downlink signals received by at least twoactivated receiver circuits, and wherein in the second state the powerloop controller is configured to generate the transmit power controlcommands based on SIR values of downlink signals received by one of atleast two activated receiver circuits.
 16. The circuit of claim 15,wherein the one of the at least two activated receiver circuits is thereceiver circuit that receives downlink signals with maximumsignal-to-interference-and-noise ratio.
 17. The circuit of claim 15,wherein the diversity controller comprises a second timer configured todetermine a length of the first state and a third timer configured todetermine a length of the second state.
 18. A circuit, comprising: apower loop controller configured to adjust a power of uplink signalstransmitted by a transmitter based on transmit power control commandsincluded in downlink signals, wherein the power loop controller isconfigured to turn the transmitter off if the quality measure fallsbelow a first threshold value; a TPC quality estimator configured toestimate a quality measure of the transmit power control commands; and adiversity controller configured to selectively activate and deactivateone or more of a plurality of receiver circuits based on the estimatedquality measure.
 19. The circuit of claim 18, wherein the power loopcontroller is configured to turn the transmitter on if the qualitymeasure exceeds a second threshold value.
 20. A method, comprising:estimating a quality of downlink signals, wherein each of the downlinksignals is derived from a respective one of a plurality of antennaports, wherein estimating the quality of the downlink signals comprisesestimating signal-to-interference-and-noise ratio (SIR) values oftransmission power control (TPC) symbols or of pilot symbols and TPCsymbols comprised in the downlink signals; selectively activating anddeactivating one or more of a plurality of receiver circuits eachcoupled to a respective one of the plurality of antenna ports; andgenerating transmit power control commands based on the estimatedquality of the downlink signals, the transmit power control commandsconfigured to request an adjustment of a power of the downlink signals.21. A method, comprising: estimating a quality measure of transmit powercontrol commands included in downlink signals; selectively activatingand deactivating one or more of a plurality of receiver circuits basedon the estimated quality measure; and adjusting a power of uplinksignals based on the transmit power control commands, wherein a power ofthe uplink signals is turned off if the quality measure falls below afirst threshold value and is turned on if the quality measure exceeds asecond threshold value.